Adhesively bonding pressure sensitive adhesive (PSA)-coated polymer films onto substrates has been carried out for a variety of purposes. One method of applying the PSA-coated polymer film to a substrate is best described as a “wet” application technique. In a wet application, the pressure sensitive adhesive layer of the film and/or the substrate is first wet with an application solution. The application solution is typically sprayed onto the surface of the substrate and pressure sensitive adhesive in a fine mist so that relatively uniform coverage of the pressure sensitive adhesive and/or substrate is obtained. The pressure sensitive adhesive layer is then brought into contact with the surface of the substrate such that a layer of application solution is present at the interface between the pressure sensitive adhesive and the substrate. The layer of application solution interrupts the adhesive bonding of the pressure sensitive adhesive layer to the substrate thereby allowing the PSA-coated film to be precisely positioned on the substrate. After the film has been positioned, the bulk of the application solution is then removed from between the pressure sensitive adhesive and the substrate by applying pressure to the polymer film, for example, using a squeegee which forces the application solution to an outer edge of the film. Once the application solution is removed, an adhesive bond is formed between the pressure sensitive adhesive and the substrate. The strength of the adhesive bond may increase over time as the remaining application solution evaporates.
Application solutions typically used in a wet application technique typically comprise a dilute (i.e., about 0.01% to about 1%-wt.) water-based solution of a wetting agent or surfactant, very commonly a household detergent or soap. The wetting agent functions to reduce the surface tension of the water thereby allowing the application solution to wet-out the surface of the substrate in a relatively continuous coating. An application solution including water, a wetting agent, and sodium chloride was reported in U.S. Pat. Appl. Pub. No. 2002/0117257 (Kubik).